My Snatch Block

I wanted to show my nephew how pulleys "reduce" the weight of things, and ended up working full-time in finding a good pulley design to print, then after printing them finding out they have high friction and hardly demonstrate the principle. So here is my design, and what it is designed to do:

The wheel is 10 cm in diameter, designed to work with what is soled around here as a simple laundry rope (semi-elastic fabric rope, about 8 mm thick when not stretched).
The wheel is designed to have a couple of 623ZZ ball bearings installed into it, such that a
3 mm shaft or screw can be used as it's axle.

The snatcher (block, handle, whatever) is designed to fit the wheel with 1/2 a mm at each side, such that the rope will not slide away from the depression in the wheel and get stuck beside the wheel.